Why do asian countries have higher cancer rate if their diets contain more allium/cruciferous vegetables (proven antitumoral effects)?

Not always diet: Most malignancies are due to carcinogens and viruses. In China, much of the food is not well controlled and carcinogens may be present in high levels in villages. Many viruses are also present. In Japan, the high level of gastric cancer was associated with the polishing of rice that for many years was accomplished with asbestos